The main objective of the proposed research is to test the hypothesis that vitamin E may regulate immune responses through altering intracellular prostaglandin and cyclic nucleotide (cAMP) levels. The immune stimulatory effect of vitamin E and its protective effect against bacterial infections has been amply demonstrated now by us and others, but the mechanism of the action remains unknown. The premise of this research is the observation that vitamine E may regulate prostaglandin biosynthesis in various tissues and cells. Prostaglandins may participate in the regulation of immunological processes and inflammatory processes via regulation of cAMP synthesis. Cyclic AMP (and perhaps cGMP) is one of the critical humoral mediators of immunologic, phagocytic and inflammatory processes. If intracellular cAMP levels are regulated by vitamin E, this might explain the immunologic effect of vitamin E. In the proposed research, we intend to study the correlation between the nutritional vitamin E level of the chicken, prostaglandin production in immunospecific organs, cAMP level in these organs and the immunologic and phagocytic performance of the chicken against bacterial infections.